JP4919082B2 - Ion beam processing apparatus and ion beam processing method - Google Patents

Description

  The present invention relates to an ion beam processing apparatus and an ion beam processing method.

  An ion beam processing apparatus such as an ion beam etching apparatus (also referred to as an ion milling apparatus) that performs etching by irradiating the surface of a workpiece such as a substrate with an ion beam is known. Such an ion beam processing apparatus includes an ion source that generates plasma and an extraction electrode that extracts ion particles from the plasma in the ion source.

For example, in the ion beam processing apparatus disclosed in Patent Document 1, an extraction electrode for extracting ion particles from an ion source is composed of three electrodes. Through holes are formed in these three electrodes, and the shape and beam diameter of the ion particles are defined by passing through the through holes of each electrode.
JP 2002-353172 A

  In the ion beam processing apparatus having the above-described configuration, when the ion beam is irradiated, the electrode located closest to the discharge vessel is heated by collision of electrons in the plasma. The remaining two electrodes are heated by thermal radiation from the electrode located closest to the discharge vessel, but the amount of heating decreases as the distance from the discharge vessel increases, so a thermal gradient occurs between the three electrodes. Therefore, each electrode bends according to the heating amount, and when the ion beam is irradiated, the positions of the through holes provided in the three electrodes are shifted, the intensity distribution of the ion beam changes, and a stable ion beam is generated. There was a problem that it could not be obtained.

  In addition, since the electrode farthest from the discharge vessel among the three electrodes faces the workpiece, scattered matter generated when the workpiece is processed accumulates. When such a deposit is peeled off, an abnormal discharge is generated between the electrodes, which hinders normal operation of the ion beam etching apparatus.

  Therefore, an object of the present invention is to provide an ion beam processing apparatus and an ion beam processing method that can irradiate a stable ion beam.

  In order to solve the above problems, the present invention includes an ion source that generates plasma, a first grid that extracts ion particles from the plasma generated in the ion source by applying a positive voltage, and a negative grid. A second grid that accelerates ion particles extracted by the first grid by applying a voltage, and ions that are provided between the second grid and the workpiece and accelerated by the second grid A third grid for emitting particles to the workpiece; an electron emitter capable of emitting electrons between the third grid and the workpiece; and extracting the ion particles in the plasma of the ion source And a control device that applies a positive voltage to the third grid and emits the electrons to the electron emitter in a state in which the electron beam is not emitted. .

  According to such an ion beam processing apparatus, in a state where ion particles in the plasma of the ion source are not extracted, the control apparatus applies a positive voltage to the third grid and causes the electron emitter to emit electrons. Therefore, the third grid can be heated by attracting and colliding the electrons emitted from the electron emitter to the third grid. On the other hand, since the first grid is heated by the collision of electrons in the plasma of the ion source, the first grid and the third grid can be heated in advance before the ion beam is extracted. Therefore, the 2nd grid located between the 1st grid and the 3rd grid is heated by radiation from the 1st grid and the 3rd grid, and it heats between the 1st grid, the 2nd grid, and the 3rd grid. Generation of a gradient can be suppressed. That is, the thermal deformation of the first grid, the second grid, and the third grid is set to the same level in advance, and the rapid temperature change and the generation of the temperature gradient are suppressed during the ion beam irradiation, and the ion beam intensity distribution changes. This can be suppressed. This makes it possible to irradiate a stable ion beam that does not change with time.

  In addition, the control device applies a positive voltage to the third grid and causes the electron emitter to emit electrons when the voltage applied to the first grid does not reach the voltage for extracting ion particles. It is preferable.

  According to such an ion beam processing apparatus, since the positive voltage is applied to the third grid when the voltage for extracting the ion particles from the ion source has not reached the first grid, the positive voltage applied to the third grid is applied. Ion particles are not extracted from the plasma of the ion source due to the influence of the voltage. Therefore, the ion beam is not accidentally emitted.

  The controller may apply a negative voltage having a smaller absolute value to the third grid than the voltage applied to the second grid when the ion particles are extracted by the first grid. preferable.

  According to such an ion beam processing apparatus, when ion particles are extracted by the first grid, a negative voltage having a smaller absolute value than the voltage applied to the second grid is applied to the third grid. The third grid draws out the ion particles, and attracts and collides with the ion particles floating around, and etches and removes the deposits deposited on the surface of the third grid. This deposit is metal scraps or the like scattered from the workpiece during processing, and causes abnormal discharge between the grids. The third grid is heated by the collision of ion particles. Therefore, the generation of a thermal gradient between the grids during ion beam irradiation is prevented, the thermal deformation of the first grid, the second grid, and the third grid is made the same, and the center of the hole formed in each grid is shifted. Can be prevented. Therefore, it is possible to suppress a change in the intensity distribution of the ion beam during ion beam irradiation, and it is possible to irradiate a stable ion beam that does not change with time.

  Further, according to the present invention, in the above-described ion beam processing apparatus, a positive voltage is applied to the third grid located closest to the workpiece among the three extraction electrodes to collide electrons emitted from the electron emitter. A preheating step for heating the third grid, an extraction step for extracting an ion beam from the ion source, and a processing step for processing a workpiece by the ion beam extracted from the ion source. An ion beam processing method characterized by the above is provided.

  According to such an ion beam processing method, in the preliminary heating step, a positive voltage is applied to the third grid, and the third grid is heated by colliding electrons emitted from the electron emitter. it can. Therefore, by heating the third grid in advance, a rapid temperature change can be suppressed when the ion beam is irradiated in the extraction process. Therefore, a stable ion beam that does not change with time can be irradiated.

  In the preliminary heating step, it is preferable to heat the first grid located closest to the ion source among the extraction electrodes by generating plasma in the ion source.

  According to such an ion beam processing method, the first grid can be heated by collision of electrons in plasma generated in the ion source. Moreover, the grid located between a 1st grid and a 3rd grid can be heated by radiation. That is, by heating the entire extraction electrode, it is possible to suppress the occurrence of a thermal gradient between the grids. Therefore, each grid of the extraction electrode can be prevented from expanding non-uniformly, and a stable ion beam can be irradiated.

  In the extraction step, it is preferable that the voltage applied to the third grid is switched to a negative voltage.

  According to such an ion beam processing method, the voltage applied to the third grid in the extraction process is switched to a negative voltage, so that the third grid extracts the ion particles from the ion source while drawing the surrounding ion particles. Make a collision. The deposits deposited on the surface of the third grid can be etched and removed by the collision of the ion particles. This deposit is metal scraps or the like scattered from the workpiece during the processing, and can prevent an abnormal discharge between the grids. The third grid is heated by the collision of ion particles. Therefore, generation of a thermal gradient between the grids can be suppressed, and a stable ion beam that does not change with time can be irradiated.

  In the preliminary heating step, it is preferable that a voltage that does not extract ion particles is applied to the first grid and the second grid.

  According to such an ion beam processing method, in the preliminary heating step, a voltage that does not extract ion particles is applied to the first grid and the second grid, so that the positive voltage applied to the third grid is applied. Ion particles are not extracted from the plasma of the ion source due to the influence of the voltage. Therefore, the ion beam is not accidentally emitted.

  In the preliminary heating step, the first grid and the second grid are preferably grounded.

  According to such an ion beam processing method, since the first grid and the second grid are grounded in the preheating step, the electric field by the third grid hardly acts on the ion particles in the ion source, and a positive voltage is generated. Ion particles are not extracted from the applied third grid. Specifically, since the first grid and the second grid are grounded, even if ion particles move from the ion source, charges are transferred by the first grid and the second grid before reaching the third grid. Since it becomes neutral, ion particles are not extracted.

  ADVANTAGE OF THE INVENTION According to this invention, the ion beam processing apparatus and ion beam processing method which can irradiate the stable ion beam can be provided.

  An ion source according to an embodiment of the present invention will be described with reference to FIGS. An ion beam etching apparatus 1 shown in FIG. 2A is an apparatus that etches a substrate 5 with an ion beam B (FIG. 1). Examples of the substrate 5 include a substrate such as a thin film magnetic head. In this case, a slider or the like of the thin film magnetic head is etched. The ion beam etching apparatus 1 includes an ion source 2 that generates an ion beam B, a processing chamber 3 that houses a substrate 5 irradiated with the ion beam B, and a standby chamber 4 that waits for a substrate 5 before processing. Yes. The ion source 2 and the processing chamber 3 communicate with each other via an extraction electrode 24 described later. The ion source 2 and the extraction electrode 24 will be described later.

  In the processing chamber 3, a substrate holder 31 that holds the substrate 5 and an electron neutralizer 32 for neutralizing the ion beam B are installed. For example, when the ion beam B is a positive ion such as Ar +, electrons are emitted from the electron neutralizer 32 and the space charge in the processing chamber 3 is neutralized. Further, a vacuum pump 33 is connected to the processing chamber 3 for evacuating the processing chamber 3 and maintaining the pressure at a predetermined pressure.

  The standby chamber 4 is provided with a substrate holding mechanism 41 that holds the substrate 5 before processing, and a gate valve 42 that can be opened and closed between the processing chamber 3. The substrate holding mechanism 41 movably holds the substrate 5 between the standby position shown in FIGS. 2A and 2C and the advanced position shown in FIG. As shown in FIG. 2B, when the substrate 5 is located at the advanced position, the substrate 5 is located in the vicinity of the substrate holder 31. At this time, the gate valve 42 is opened, and the processing chamber 3 and the standby chamber 4 are in communication. On the other hand, as shown in FIGS. 2A and 2C, when the substrate 5 is positioned at the standby position, the gate valve 42 is closed, and the processing chamber 3 and the standby chamber 4 are completely independent. It becomes. The vacuum pump 33 is also connected to the standby chamber 4 and can maintain the interior of the standby chamber 4 at a predetermined pressure.

  The ion source 2 shown in FIG. 1 includes a vacuum vessel 20, a discharge vessel 21 having an opening 21a, a coil 22 provided outside the discharge vessel 21, and a high-frequency power supply 61 that supplies high-frequency power to the coil 22. And an extraction electrode 24 for extracting ions in the plasma P generated in the discharge vessel 21 from the opening 21a to generate an ion beam B. As shown in FIG. 2A, the vacuum container 20 is connected to the vacuum pump 33 via the processing chamber 3, and is formed in a cylindrical shape by stainless steel or the like.

  As shown in FIG. 1, the discharge vessel 21 is disposed in the vacuum vessel 20. The discharge vessel 21 is formed of a dielectric material such as quartz or aluminum oxide into a cylindrical shape having an opening 21a below the figure. On the upper surface of the discharge vessel 21 in FIG. 1, a supply port 21 b for supplying the source gas from the source gas supply device 23 into the discharge vessel 21 is provided. In this embodiment, argon gas is used as the source gas.

  The coil 22 is provided inside the vacuum vessel 20 and outside the discharge vessel 21. The coil 22 is provided so that the axis is located in the discharge vessel 21. The coil 22 is connected to the high frequency power supply 61 via the matching unit 62. The high frequency power supply 61 is, for example, a high frequency power supply or a high frequency amplifier. The frequency of the high frequency power supply 61 is several MHz to several tens of MHz (for example, 2 to 13.5 MHz), and is about 4 MHz in the present embodiment. The high frequency power supply 61 applies, for example, 200 to 2000 W of power to the coil 22 according to the capacity and shape of the discharge vessel 21.

  The extraction electrode 24 has a screen grid 25, an acceleration grid 26, and a deceleration grid 27. The screen grid 25, the acceleration grid 26, and the deceleration grid 27 are metal plates each having a plurality of holes. The screen grid 25, the acceleration grid 26, and the deceleration grid 27 are arranged in order from the inside to the outside of the discharge vessel 21, and each grid is integrated by screws (not shown) while maintaining a predetermined interval via a spacer (not shown). Fixed.

  The screen grid 25 is provided in the opening 21 a of the discharge vessel 21 and separates the plasma P and the acceleration grid 26. The screen grid 25 is an electrode that extracts ion particles from the plasma P generated in the ion source 2. The screen grid 25 is connected to a DC power source 63 for continuously applying a positive high voltage, and a voltage of 400 to 1500 V, for example, can be applied. The ion beam energy of the ion beam B is determined by the voltage applied to the screen grid 25.

  The acceleration grid 26 is an electrode that accelerates ion particles extracted by the screen grid 25 by applying a negative voltage. A DC power source 64 for continuously applying a negative high voltage is connected to the acceleration grid 26, and a voltage of −200 to −1000 V, for example, can be applied.

  The deceleration grid 27 is an electrode that is provided between the acceleration grid 26 and the substrate holder 31 and discharges ion particles accelerated by the acceleration grid 26 to the substrate 5 on the substrate holder 31. The deceleration grid 27 is connected to a bipolar power source 65 that can apply positive and negative voltages.

  The extraction electrode 24 can control the ion beam diameter of the ion beam B within a predetermined numerical range using the lens effect by adjusting the potential difference between the acceleration grid 26 and the deceleration grid 27. The high-frequency power supply 61, the matching unit 62, the DC power supply 63, the DC power supply 64, the bipolar power supply 65, and the like described above are controlled by the control device 6. The control device 6 further controls the source gas supply device 23 and the electron neutralizer 32 to cause the beam etching device 1 to perform an etching process (milling process).

  Next, the etching process executed in the ion beam etching apparatus 1 described above will be described with reference to the drawings of FIGS. 2A to 2C and the flowcharts of FIGS. The etching process is a process of etching the substrate 5 with the ion beam B. When the substrate 5 to be processed is held by the substrate holding mechanism 41 of the standby chamber 4, the etching process starts. As shown in FIG. 3, the etching process performs the preparation process (S 1), the substrate placement process (S 2), and the processing process (S 3), performs the substrate removal (S 4), and ends.

  In the preparation step shown in FIG. 4, first, a raw material gas that is a material for generating plasma P is supplied to the ion source 2 and the processing chamber 3 (S11). Specifically, the source gas is supplied into the discharge vessel 21 of the ion source 2 by the source gas supply device 23 (FIG. 1) and supplied into the processing chamber 3 through the extraction electrode 24. When the raw material gas is supplied, the standby chamber 4 is evacuated by the vacuum pump 33 (S12), and the plasma P is easily generated in the discharge vessel 21 by the electron neutralizer 32 in the processing chamber 3. Electrons for generation start to be emitted (S13). Subsequently, a voltage is applied to the coil 22 from the high frequency power supply 61 (S14). As a result, an electromagnetic field is generated by the coil 22 in the discharge vessel 21, and plasma P is generated in the discharge vessel 21.

  When the plasma P is generated in the discharge vessel 21, a voltage is applied to each grid 25-27 of the extraction electrode 24 (S15). Specifically, a floating voltage is applied to the screen grid 25 and the acceleration grid 26, and a positive voltage is applied to the deceleration grid 27. The floating voltage is a voltage at which the screen grid 25 and the acceleration grid 26 do not extract ion particles from the plasma P in the discharge vessel 21. In the present embodiment, the screen grid 25 and the acceleration grid 26 are grounded and set to 0V. That is, in S15, the control device 6 applies a positive voltage to the deceleration grid 27 in a state in which the ion particles in the plasma P of the ion source 2 are not extracted by grounding the screen grid 25 and the acceleration grid 26. Yes. Further, the control device 6 causes the electron neutralizer 32 to emit electrons into the processing chamber 3, specifically between the deceleration grid 27 and the substrate holder 31.

  At this time, the electrons emitted from the electron neutralizer 32 are attracted to and collide with the deceleration grid 27. The deceleration grid 27 is heated by the collision of electrons. On the other hand, the screen grid 25 is heated by the collision of electrons in the plasma P in the discharge vessel 21. That is, before extracting the ion beam B, the screen grid 25 and the deceleration grid 27 can be heated in advance. Since the acceleration grid 26 positioned between the screen grid 25 and the deceleration grid 27 is heated by radiation from the screen grid 25 and the deceleration grid 27, heat is generated between the screen grid 25, the acceleration grid 26, and the deceleration grid 27. Generation of a gradient can be suppressed. Therefore, by heating the screen grid 25, the acceleration grid 26, and the deceleration grid 27 in advance, the thermal deformation of each of the grids 25 to 27 is kept at the same level, and a rapid temperature change is suppressed when the ion beam is irradiated. can do. During ion beam irradiation, it is possible to suppress rapid temperature changes and temperature gradients, and to suppress changes in the intensity distribution of the ion beam. This makes it possible to irradiate a stable ion beam that does not change with time.

  Further, since the positive voltage is applied to the deceleration grid 27 when the screen grid 25 and the acceleration grid 26 are at the floating potential, ion particles are not emitted from the deceleration grid 27. Specifically, since the screen grid 25 and the acceleration grid 26 are grounded, ion particles are not extracted from the plasma P of the ion source due to the influence of a positive voltage applied to the deceleration grid 27. Therefore, the ion beam is not accidentally emitted. Even if the ion particles move, since the charges are transferred and neutralized by the screen grid 25 and the acceleration grid 26 before reaching the deceleration grid 27, the ion particles are not drawn out from the deceleration grid 27.

  Next, it is determined whether the evacuation of the standby chamber 4 is completed (S16). If the evacuation has not been completed yet (S16: NO), a voltage is continuously applied to each of the grids 25 to 27 (S15). When the evacuation is completed (S16: YES), application of voltage to the coil 22 and emission of electrons from the electron neutralizer 32 are stopped (S17), and application of positive voltage to the deceleration grid 27 is stopped. (S18). Then, the supply of the source gas to the ion source 2 and the processing chamber 3 is stopped (S19).

  The substrate placement step shown in FIG. 5 is a step of placing the substrate 5 at a position where it can be etched by an ion beam. First, the substrate 5 is transferred from the standby chamber 4 to the processing chamber 3 by the substrate holding mechanism 41 (S21). Specifically, the closed gate valve 42 is opened, the substrate holding mechanism 41 is moved from the standby position (FIG. 2A) to the advanced position (FIG. 2B), and the substrate 5 is moved to the substrate holder. 31. When the transfer of the substrate 5 is not yet completed, that is, when the substrate 5 is not held by the substrate holder 31 (S22: NO), the substrate 5 is subsequently transferred (S21). When the substrate 5 is held by the substrate holder 31, it is determined that the transfer of the substrate 5 is completed (S22: YES), the substrate holder 31 is tilted by a predetermined angle, and the angle is adjusted (S23).

  The processing step shown in FIG. 6 is a step of processing the substrate 5 by an ion beam extracted from the ion source. First, source gas is supplied to the ion source 2 and the processing chamber 3 (S31), and electrons are emitted from the electron neutralizer 32 (S32). Next, a voltage is applied to the coil 22 from the high frequency power supply 61 (S33), and plasma P is generated in the discharge vessel 21 of the ion source 2. In the state where the plasma P is generated, a voltage is applied to each grid of the extraction electrode 24 (S34). Specifically, as described above, the screen grid 25 is applied with a positive voltage from the DC power supply 63, and the acceleration grid 26 is applied with a negative voltage from the DC power supply 64. The deceleration grid 27 is applied with a negative voltage from the bipolar power supply 65. The voltage applied to the deceleration grid 27 is a negative voltage having a smaller absolute value than the voltage applied to the acceleration grid 26 and substantially equal to zero. Then, an ion beam is emitted (S35), and a predetermined etching process is performed on the substrate 5 (S36). At this time, the ion beam is spatially neutralized by electrons emitted from the electron neutralizer 32. When the processing step is finished, the processed substrate 5 is taken out from the processing chamber 3 (FIG. 3, S4), and the etching process is finished.

  In the processing step, when ion particles are drawn out by the screen grid 25, a negative voltage having a smaller absolute value than the voltage applied to the acceleration grid 26 is applied to the deceleration grid 27. While extracting the ion particles, the ion particles floating in the processing chamber 3 are attracted to the deceleration grid 27 and collide with the deceleration grid 27, whereby the deposits deposited on the surface of the deceleration grid 27 can be etched and removed. (See FIG. 2 (c)). This deposit is metal scraps or the like scattered from the substrate 5 during processing, and causes abnormal discharge between the grids. Moreover, the deceleration grid 27 is heated by collision of ion particles. Therefore, generation of a thermal gradient between the screen grid 25, the acceleration grid 26, and the deceleration grid 27 is prevented, and the thermal deformation of the screen grid 25, the acceleration grid 26, and the deceleration grid 27 is made the same, and the grids 25 to 27 are formed. The center of the hole can be prevented from shifting, and the ion beam intensity distribution can be prevented from changing during ion beam irradiation. Therefore, a stable ion beam that does not change with time can be irradiated. In addition, since the screen grid 25 and the deceleration grid 27 are preliminarily heated in the preparation process, it is possible to shorten the time required to stabilize the temperatures of the grids 25 to 27 in the machining process.

  In S15 and S34, the optimum voltage is selected for the voltage applied to the deceleration grid 27 according to the material of the workpiece, the machining conditions, and the like.

  The ion beam processing apparatus and the ion beam processing method according to the present invention are not limited to the above-described embodiments, and various modifications and improvements can be made. For example, in the above-described embodiment, the case where the substrates 5 are processed one by one has been described as an example, but a plurality of substrates may be processed simultaneously.

  In the above-described embodiment, the outer periphery of the three grids 25 to 27 is fixed by screws (not shown) in the extraction electrode 24. However, the extraction electrode 24 may have the same configuration at the center as well as the outer periphery. A frame that fixes the outer periphery may be provided.

  In the above-described embodiment, the screen electrode 25 and the acceleration grid 26 are grounded in S15 (FIG. 4) of the preparation step. However, the ion particles are extracted from the discharge vessel 21 to the screen electrode 25 and the acceleration grid 26. You may apply the voltage which is not.

  The present invention can be suitably used for an ion beam irradiation apparatus such as an etching apparatus or a sputtering apparatus.

Explanatory drawing which shows the ion source of the ion beam etching apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows operation | movement of the ion beam etching apparatus which concerns on embodiment of this invention, (a) is the time of a preparatory process, (b) is a board | substrate arrangement | positioning process, (c) is a figure which shows the time of a process process. . The flowchart which shows the etching process of the ion beam processing method of this invention. The flowchart which shows the preparatory process of the etching process of the ion beam processing method of this invention. The flowchart which shows the board | substrate arrangement | positioning process of the etching process of the ion beam processing method of this invention. The flowchart which shows the process process of the etching process of the ion beam processing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion beam etching apparatus 2 Ion source 3 Processing chamber 4 Standby chamber 5 Substrate 6 Controller 20 Vacuum vessel 21 Discharge vessel 21a Opening 21b Supply port 22 Coil 23 Ion gas supply device 24 Extraction electrode 25 Screen grid 26 Acceleration grid 27 Deceleration grid 31 Substrate holder 32 Electronic neutralizer 33 Vacuum pump 41 Substrate holding mechanism 42 Gate valve 61 High frequency power source 62 Matching device 63, 64 DC power source 65 Polar power source

Claims (8)

An ion source for generating plasma;
A first grid for extracting ion particles from the plasma generated in the ion source by applying a positive voltage;
A second grid for accelerating ion particles extracted by the first grid by applying a negative voltage;
A third grid that is provided between the second grid and the workpiece and releases ion particles accelerated by the second grid to the workpiece;
An electron emitter capable of emitting electrons between the third grid and the workpiece;
An ion beam processing apparatus comprising: a control device that applies a positive voltage to the third grid and emits the electrons to the electron emitter in a state where the ion particles in the plasma of the ion source are not extracted. .   The controller applies a positive voltage to the third grid and causes the electron emitter to emit electrons when the voltage applied to the first grid does not reach the voltage for extracting ion particles. The ion beam processing apparatus according to claim 1, wherein   The control device applies a negative voltage having an absolute value smaller than a voltage applied to the second grid to the third grid when the ion particles are extracted by the first grid. The ion beam processing apparatus according to claim 1. In the ion beam processing apparatus according to claim 1,
A preheating step of heating the third grid by applying a positive voltage to the third grid located closest to the workpiece among the three extraction electrodes and colliding electrons emitted from the electron emitter. When,
An extraction step of extracting an ion beam from the ion source;
A processing step of processing a workpiece with an ion beam extracted from the ion source.   5. The ion beam processing method according to claim 4, wherein in the preliminary heating step, plasma is generated in the ion source to heat a first grid located closest to the ion source among the extraction electrodes. 6. .   6. The ion beam processing method according to claim 4, wherein in the extraction step, a voltage applied to the third grid is switched to a negative voltage.   In the preheating step, a voltage that does not extract ion particles is applied to the first grid and the second grid positioned between the first grid and the third grid. The ion beam processing method according to claim 4. The said preheating process WHEREIN: The 2nd grid located between the said 1st grid and the said 1st grid and the said 3rd grid is earth | grounded, The Claim 1 thru | or 6 characterized by the above-mentioned. Ion beam processing method.

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